Beijing University of Posts and Telecommunications

About: Beijing University of Posts and Telecommunications is a education organization based out in Beijing, Beijing, China. It is known for research contribution in the topics: MIMO & Quality of service. The organization has 39576 authors who have published 41525 publications receiving 403759 citations. The organization is also known as: BUPT.

−60 °C solution synthesis of atomically dispersed cobalt electrocatalyst with superior performance

Abstract: Temperature can govern morphologies, structures and properties of products from synthesis in solution. A reaction in solution at low temperature may result in different materials than at higher temperature due to thermodynamics and kinetics of nuclei formation. Here, we report a low-temperature solution synthesis of atomically dispersed cobalt in a catalyst with superior performance. By using a water/alcohol mixed solvent with low freezing point, liquid-phase reduction of a cobalt precursor with hydrazine hydrate is realized at −60 °C. A higher energy barrier and a sluggish nucleation rate are achieved to suppress nuclei formation; thus atomically dispersed cobalt is successfully obtained in a catalyst for oxygen reduction with electrochemical performance superior to that of a Pt/C catalyst. Furthermore, the atomically dispersed cobalt catalyst is applied in a microbial fuel cell to obtain a high maximum power density (2550 ± 60 mW m−2) and no current drop upon operation for 820 h. Rapid nucleation and growth hinder the formation of atomically dispersed metals on solid supports in solution. Here the authors report a low-temperature solution-phase synthesis for isolated cobalt atoms on nitrogen-doped carbon, with electrocatalytic activity for oxygen reduction in a microbial fuel cell.

Greatly Enhanced Anticorrosion of Cu by Commensurate Graphene Coating.

Abstract: Metal corrosion is a long-lasting problem in history and ultrahigh anticorrosion is one ultimate pursuit in the metal-related industry. Graphene, in principle, can be a revolutionary material for anticorrosion due to its excellent impermeability to any molecule or ion (except for protons). However, in real applications, it is found that the metallic graphene forms an electrochemical circuit with the protected metals to accelerate the corrosion once the corrosive fluids leaks into the interface. Therefore, whether graphene can be used as an excellent anticorrosion material is under intense debate now. Here, graphene-coated Cu is employed to investigate the facet-dependent anticorrosion of metals. It is demonstrated that as-grown graphene can protect Cu(111) surface from oxidation in humid air lasting for more than 2.5 years, in sharp contrast with the accelerated oxidation of graphene-coated Cu(100) surface. Further atomic-scale characterization and ab initio calculations reveal that the strong interfacial coupling of the commensurate graphene/Cu(111) prevents H2 O diffusion into the graphene/Cu(111) interface, but the one-dimensional wrinkles formed in the incommensurate graphene on Cu(100) can facilitate the H2 O diffusion at the interface. This study resolves the contradiction on the anticorrosion capacity of graphene and opens a new opportunity for ultrahigh metal anticorrosion through commensurate graphene coating.

Yolk-Shell Sn@C Eggette-like Nanostructure: Application in Lithium-Ion and Sodium-Ion Batteries.

Abstract: Yolk-shell carbon encapsulated tin (Sn@C) eggette-like compounds (SCE) have been synthesized by a facile method. The SCE structures consist of tin cores covered by carbon membrane networks with extra voids between the carbon shell and tin cores. The novel nanoarchitectures exhibit high electrochemical performance in both lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). As anodes for LIBs, the SCE electrodes exhibit a specific capacity of ∼850 mA h g(-1) at 0.1 C (100 mA g(-1)) and high rate capability (∼450 mA h g(-1) remains) at high current densities up to 5 C (5000 mA g(-1)). For SIBs, the SCE electrodes show a specific capacity of ∼400 mA h g(-1) at 0.1 C and high rate capacity (∼150 mA h g(-1) remains) at high current densities up to 5 C (5000 mA g(-1)).

Adaptive optimal transmit power allocation for two-hop non-regenerative wireless relaying system

Abstract: In order to combat fading in wireless networks and increase the capacity of a system, cooperation is allowed among the terminals in a network. The adaptive optimal power allocation (PA) scheme, based on a certain system performance, is an important issue for relaying routing and network operation. The paper analyzes the two-hop non-regenerative (NR) relaying channel with and without diversity, and investigates the optimal PA scheme between the source terminal (Tx) and the relaying terminal (RS) under power constraints. Since, in real relaying environments, the transmitter usually knows the instantaneous channel state information (ICSI) of the 1st hop and the statistical channel state information (SCSI) of the 2nd hop, the proposed PA schemes are based on two-hop ICSI and two-hop mixed channel state information (MCSI) respectively. With the adaptive scheme, the system performance not only outperforms that of the direct transmission system, but also obtains the maximum channel capacity or SNR of the relaying system.

Distributed Blockchain-Based Trusted Multidomain Collaboration for Mobile Edge Computing in 5G and Beyond

Abstract: Mobile edge computing (MEC) sinks computing power to the edge of networks and integrates mobile access networks and Internet services in 5G and beyond. With the continuous development of services, privacy protection is extremely important in a heterogeneous MEC system for multiserver collaboration. However, most of the existing schemes only consider the privacy of users or services other than the privacy of network topology. For the purpose of topology privacy protection, this article employs blockchain to construct heterogeneous MEC systems and adopts accommodative bloom filter as a carrier for multidomain collaborative routing consensus without exposing topology privacy. Blockchain is used to implement multiplex mutual trust networking and collaborative routing verification through the membership service and consensus mechanism. Experiments are conducted to evaluate the feasibility and performances of our scheme. The results indicate that the proposed scheme can highly improve the credibility and efficiency of MEC collaboration.